A nucleus ᵐₙ X emits one α- particle and two β- particles. The resulting nucleus is

Options

(a) ᵐ⁻⁶ₙ₋₄ Z
(b) ᵐ⁻⁶ₙ Z
(c) ᵐ⁻⁴ₙ X
(d) ᵐ⁻⁴ₙ₋₂ Y

Correct Answer:

ᵐ⁻⁴ₙ X

Explanation:

When ᵐₙ X emits one α- particle then its atomic mass decreases by 4 units and atomic number4 by 2. Therefore, the new nucleus becomes ᵐ⁻⁴ₙ₋₂ Y. But as it emits two β⁻ particles, its atomic number incre4ases by 2. Thus the resulting nucleus is ᵐ⁻⁴ₙ X.